Actions

Tutorial Objective

Demonstrate basic Actor Action using LibGDX Scene2D

• MoveByAction
• RotateAction
• ScaleByAction
• SequenceAction
• ParallelAction

By the end of the tutorial you will have the following:

What you should be familiar with for this tutorial

• What a Stage is and how to add an Image to it (See basic Image Tutorial)

What you will need to do this tutorial

• Install LibGDX  & Create Sample Application (See getting started instructions)

Actor Action basic

You can add an Action to all type of Scene2D Actor: Button, Image, Group..

There is two ways to add an Action:

• Shorthand: More compact but harder to read when combining actions
• Full declaration: Easier to read but takes lot of space.

Shorthand

The following shorthand Action makes an object move to a given position:

anActor.addAction(Actions.moveTo(x,y,time));

Full declaration

Equivalent Action fully declared:

MoveToAction action = new MoveToAction();
action.setDuration(duration);
action.setPosition(x,y);
actor.addAction(action);

Code

Full Code available for download here or can be read below.

public class MyGdxGame extends ApplicationAdapter {
  private Stage stage;

  @Override
  public void create () {
    stage = new Stage(new ScreenViewport());
    Texture texture = new Texture(Gdx.files.absolute("image.jpg"));

    int X_left= Gdx.graphics.getWidth()/3-texture.getWidth()/2;
    int X_right = Gdx.graphics.getWidth()*2/3-texture.getWidth()/2;
    int Y_top = Gdx.graphics.getHeight()*2/3-texture.getHeight()/2;
    int Y_bottom = Gdx.graphics.getHeight()/3-texture.getHeight()/2;

    Image image1 = new Image(texture);
    image1.setPosition(X_left,Y_top);
    image1.setOrigin(image1.getWidth()/2,image1.getHeight()/2);
    stage.addActor(image1);

    ParallelAction topLeftRightParallelAction = new ParallelAction();
    topLeftRightParallelAction.addAction(Actions.moveTo(X_right,Y_top,1,Interpolation.exp5Out));
    topLeftRightParallelAction.addAction(Actions.scaleTo(2,2,1,Interpolation.exp5Out));

    MoveToAction moveBottomRightAction = new MoveToAction();
    moveBottomRightAction.setPosition(X_right,Y_bottom);
    moveBottomRightAction.setDuration(1);
    moveBottomRightAction.setInterpolation(Interpolation.smooth);

    ParallelAction bottomLeftRightParallelAction = new ParallelAction();
    bottomLeftRightParallelAction.addAction(Actions.moveTo(X_left,Y_bottom,1,Interpolation.sineOut));
    bottomLeftRightParallelAction.addAction(Actions.scaleTo(1,1,1));

    ParallelAction leftBottomTopParallelAction = new ParallelAction();
    leftBottomTopParallelAction.addAction(Actions.moveTo(X_left,Y_top,1,Interpolation.swingOut));
    leftBottomTopParallelAction.addAction(Actions.rotateBy(90,1));

    SequenceAction overallSequence = new SequenceAction();
    overallSequence.addAction(topLeftRightParallelAction);
    overallSequence.addAction(moveBottomRightAction);
    overallSequence.addAction(bottomLeftRightParallelAction);
    overallSequence.addAction(leftBottomTopParallelAction);

    RepeatAction infiniteLoop = new RepeatAction();
    infiniteLoop.setCount(RepeatAction.FOREVER);
    infiniteLoop.setAction(overallSequence);
image1.addAction(infiniteLoop);
  }
  @Override
  public void render () {
    Gdx.gl.glClearColor(1, 1, 1, 1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
    stage.act();
stage.draw();
  }
}

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